Self-cleaning electrical switch contact

ABSTRACT

An electrical switch including a movable switch arm, a switch contact engageable and movable with said switch arm to close an electric circuit, and wherein the contact is spring-biased to constantly engage within a seat and to wipe therein upon engagement and disengagement of said switch arm, and to return the contact to its original position.

X R 6 5 l O 0 2 g a movable switch References Cited UNITED STATES PATENTS tch contact engageable and movable with said close an electric circuit, and wherein the cong-biased to constantly engage within a seat and to n upon engagement and disengagement of said ......................200/l66BD, ZOO/56R, ZOO/164R, 200/166BH l-l0lh 1/18 200/56 (R),

166 (D), 166 (J), 166 (BD),

Frank W. Murphy;- Frank W. Murphy, Jr., 3131 S. Sheridan P.0. Box 45248, Tulsa, Okla. 74145 3,112 Jan. 15, 1970 [45] Patented May 18, 1971 CONTACT 10 Claims, 7 Drawing Figs. 52] Field of United States Patent [72] Inventors 21 AppLNo.

221 Filed 54 SELF-CLEANING ELECTRICAL swn Patented May 18,1911

FIG 1 -/NVENTORS FRANK W MURPHY FRANK W MURPHY, JR.

ATTORNEYS SELF-CLEANING ELECTRICAL SWITCH CONTACT BACKGROUND OFTHEINVENTION support means for wiping movement therein andwhich'is biased for constant engagement with its seat to frictionally remove or scrape away any film or oxide which might impede or isolate current flow.

2. Description of the Prior Art Wiping switches are not, per se, new in the art. Examples are to be found in the US. Pat. to Arthur Hall, U.S. Pat. No. 2,1 15,069, and in the patent to Kingman N. Donally, U.S. Pat. No. 2,154,670. But these patentees, as'well as others, have not been faced with the problem of maintainingthe switches-of monitoring switch gauges installed, for example, on an offshore oil drilling operation, in sour gas-(H S') areas, and/or in corrosive atmospheres. Insofar as the prior art is known,- the wiping switches heretofore developed have been largely designed to operate in normally clean aircon'ditions, but the contacts of such standard switches have failed when field tested in the areas referred to above, especially in a severely corrosive area.

SUMMARY OFTHE INVENTION The instant invention relates to the provision of a self-cleaning or wiping electric switch contactincluding apin mounted for swivel movement in a seat, the pin beingdisposed in the path of movement of a movable switch arm 'to'com'pletean electric circuit upon engagement by the switch'arm, the pin swiveling to wipe in its seat upon the continued movement of the switch arm; and, means biasingthe pin for constant engagement with its seat as-well as to efiect the return of the pin to its normal position relative to its seat upon disengagement of the switch arm therewith, while again wiping in itsseat as the pin swivels during its returnmovemen't.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a front elevational view of a conventional pressure indicating gauge and illustrating the adjustable fixed switch arms together with the electric contacts constructed in accordance with this invention;

FIG. 2 is an enlarged perspective view of the wiping switch contact shown in FIG. 1 constructed in accordance with this invention;

FIG. 3 is a fragmentary detail cross-sectional view, FIG. 3 being taken substantially on the line 3-3 of FIG. 1, looking in DESCRIPTION OF THE FIRST, PREFERRED EMBODIMENT Referring now more specifically to the drawing, reference numeral designates a conventional pressure gauge for monitoring pumps, steam generators, air and gasgene'rators, and for connection in other installations or systems wherein pressure is a variable or controlling factor. Such gauges are available on the open market and are manufactured by the Frank W. Murphy Manufacturer, Inc., 3131 'South Sheridan", Post Office Box 45248, Tulsa, Okla., and aresold under the registered trademark SWICI-IGAGE. Such gauges are to be found in. their OPL series, and include gauges for installation in vacuum lines as well as in positive pressure systems. It will be understood that similar gauges are also manufactured for monitoring other mediums, such as oil pressures, temperatures, et cetera. However, since these gauges, per se, do not form the gist of this invention, reference to the same will be made only for the purpose of providing a suitable background to demonstrate the utility of the present invention. Therefore, only a brief description of this gauge is offered below.

The gauge 10 is preferably enclosed in a die-cast aluminum case 12 whichis sealed'against weather and dust by conventional means. Scale means 14, calibrated for the function the 7 gauge is to perform, is carried on the dial faceplate l6, and laterally spaced from the dial faceplate is a transparent window 18 which is suitably supported on the case 12. A pipe fitting 20 connects the gauge 10 with a pressure line to be monitored.

Reference numeral-22 designates a shaft which extends transversely through the dial faceplate 16, and which is journaled for rotation therein. As is seen in FIG. 3, the shaft 22 has an end 22A in which is formed an inwardly extending coaxial tapped opening 228 to receive the shank 24 of a screw 26 having an enlarged-head 28. In the usual manner, the shank 24 extends transversely through an indicating-pointer movable switch arm 30 intermediate its ends, and the head 28 clampingly secures the pointer against the adjacent end of the shaft 22. The arrangement is such that as the shaft 22 turns in response to the medium the gauge is monitoring, the indicating-pointer switch arm 30 will sweep the scale 14. It is preferable that the indicating-pointer switch arm 30 be formed of nickel silver and be gold plated.

The shaft 22 turns through a geared movement responsive to changes of line pressure and, of course, the indicatingpointer switch arm 30 moves in accordance therewith to provide visual data relating to the line pressure.

Mounted onthe window 18 is a pair of rotatably adjustable compound fixed switch arms 32, 34 of identical construction and'which comprise the subject matter of the instant invention. Hence, a description of one will suffice for the other.

Thus, and with specific reference to the fixed switch arm 32, the arm is seen to comprise anelongated substantially flat metallic element 38 preferably formed of nickel silver and gold plated. The configuration of the element is essentially rectangular and includesa central bight portion 40 from the opposed ends of which longitudinally project arms 42, 44, respectively, diverging away from one another. The arms 42, 44 at their remotely disposed ends, terminate in enlarged flat, rounded ends 46, 48, respectively. In this first'preferred embodiment, one side of the end '46 is formed with an inwardly extending substantially concentric frustoconical bore 50 having' the plane of its frustum coincident with the plane of the frustum of a truncated concave switch contact seat 52 which extends inwardly from its opposed side, see FIGS. 3 and 6. The bases of the bore 50 and of the seat 52 are concentric, with the diameter of the base being greater than the diameter of the bore.

At 54 is indicated a fixed switch contact for swivel movement in the seat 52. This contact is formed of nickel silver and isalsogold plated. The contact 54 comprises an elongated cylindrical pin 56 having an integrally formed radially projectingwipingflange 58 disposed intermediate its ends. As is seen in the drawing, the flange 58 is dispcsed adjacent to but is spaced inwardly from the pin end 60 a greater distance than from the pin end 62. That side 64 of the flange 58 facing in the direction of the end 60is planar while its opposed side 66 is convex-on a radius corresponding'to the radius on which the concave seat 52 is formed. In assembly, the convex side 66 of the flange '58 seats flush against its seat 52 with the end 62 extending through the opening 50 to project beyond the adjacent side of thearm 42. The pin 56 is normally coaxial with respect to the bore 50 and seat 52. The switch contact 54 is held assembled with the arm 42 by means to be described.

Referring to FIGS. 2 and 3, it is seen that one end of an elongated flexible and resilient wire spring 67 is soldered or otherwise secured by conventional means 68 to the arm 44 adjacent the bight portion 40. The other end of the wire 67 extends transversely and loosely through an opening 70 formed in the bight portion 40, and extends longitudinally and axially over the arm 42 for reception through a diametrically extending opening 72 formed in the pin 56 intermediate its flange 58 and end 62. The connection is such that the pin 56 is constantly biased for movement to the right, as viewed in FIG. 3, to urge the flange 58 to seat in its seat 52. Preferably, the connection of the wire in the opening 72 may be somewhat loose to provide a relatively large turning area for the pin 56,

although this is not a critical feature. The pin end 62 and wire 67 may be rigidly connected, if desired, by mechanical means (solder, for example) without impairing this inventive concept.

The adjustable switch arms 32, 34 are mounted on the window 18 by providing the rounded end 48 of each one thereof with a transversely extending coaxial opening 74 to receive screw means 76 therethrough. The screw means 76 is formed with a smooth end portion 78 and a threaded end portion 80.

The end portion 78, adjacent its outer terminus 80, is formed with an integral radially extending wrench head 82, and the end portion 78 extending between the head 82 and the terminus 80 is received within the opening 74 after which the terminus is peened or flattened to form an enlarged shoulder 84 clamping the arm 44 against the adjacent side of the head 82.

A flat connector bar 85 having an end 86 apertured at 87 is mounted on the smooth portion 78 with a side thereof engaging the other side of the head 82. The free end of the screw means 76 is now passed through an opening 88 in which the smooth portion 78 is rotatably journalecl and which also receives a gasket 90 having a side fitting flush against the exterior side of the window 18.

In describing the operation of the gauge 10, let it be assumed that it is already monitoring the pressure in a line (not shown) presently operated at IO p.s.i. as the indicator-pointer switch arm 30 presently shows in FIG. 1. Let it be further assumed that the pressure system may operate satisfactorily at pressures of between 8 and 16.5 p.s.i. The pin 56 of the switch arm 32 is centered on a radial passing through the numeral 8 of the scale 14, and the pin 56 of the switch arm 34 is similarly located on a radial passing through a reading of 16.5. In accordance with the teachings of this invention, the closing of the switch arm 30 against either of the pins 56 will close a normally open electric circuit to energize an alarm device or shutdown mechanism for the system being monitored when the line pressure falls off or tends to exceed the predetermined pressures of 8 and 16.5 p.s.i., respectively.

FIG. 7 schematically illustrates a simple circuit controlled by the gauge for energizing an alarm or shutdown. It involves only a series circuit wherein the switch arm is connected to ground G common to the ground G connected to one side of the battery B. The other side of the battery connects to one side of the load L (signal means), and the other side of the battery connects with one side of the normally closed lockout switch 106 mounted on the casing 12. This switch is manually operable. The other side of the switch 106 is connected at 300 to a wire 302 which connects together the connector bars 85, 85. Now when the switch arm 30 closes against either one of the pins 56 of the switch arms 32, 34, a series circuit is completed and the alarm circuit is energized. The lockout switch (conventional in the art) is then opened until the engagement of the switch arm 30 with the contacted pin 56 is broken, after which it is closed to ready the alarm circuit. Quite obviously, the connector bars could be connected in special and separate circuits as desired. This is all conventional and common practice in this art.

Now let the apparatus be examined in the light of the diagrammatic showing of FIG. 6. The switch arm 30 is here illustrated as moving to the left to close against the pin 56 of, for example, the switch arm 32 to engage against the side thereof making contact at the arrowhead A. This instantly energizes the alann circuit described above. Now if the pressure falls further, the switch arm 30 pushes against the pin 56 causing it to move through an arcuate path while the convex side 66 of the flange 58 swivels and wipes in its seat 52. The wipe area extends between arrowed lines I3-B and this is limited by the engagement of the pin 56 against the inner side of the bore 50 as it swings through the are C. This movement is resisted by the tension of the wire spring 67 which, as soon as the normal operating pressure has been restored and the engagement between the switch arm 30 and the pin 56 has been broken, causes the pin 56 to swivel and wipe in a reverse direction until the axis of the pin 56 regains its normal coaxial position relative to the axes of the bore and seat associated therewith. Obviously, if the pressure in the monitored line exceeds 16.5 p.s.i., the switch am 30 will engage the pin 56 of the switch arm 34 and will again effect a closing of the alarm circuit in the manner described above. The same wiping action takes place as this pin is moved out of its normal position and is returned thereto under the influence of the spring tension exerted by the wire spring 67. The lockout switch 106 is returned to its closed position, it being assumed that it has moved to its open position after the alarm sounded, and the apparatus is again ready for service.

DESCRIPTION OF THE SECOND PREFERRED EMBODIMENT The second preferred embodiment is illustrated in FIGS. 4 and 5. Since the basic components of this embodiment are the same as those of the first, the same reference numerals are used for identical elements, except that in the second embodimerit, a prime mark has been added thereto to permit differentiation.

Essentially, the second embodiment differs from the first only in the elimination of the wire springs 67 and the substitution of flexible resilient leaf springs 200 therefor. The leaf springs 200 each have the same general configuration as the adjustable fixed switch arms 32, 34, that is, each is substantially rectangular and is bent intermediate its ends to form a bight portion 202 from the opposed ends of which diverge longitudinally extending arms 204, 206. The arm 206 terminates in a rounded end 208 that is formed with a concentric opening 210 which is received on the portion 78'. Thereafter, the switch arm 32 is also mounted on the portion 78 and the end peened over as at 84' to clampingly engage the assembly against the head 82'. The arms 44, 206 and rounded ends 48, 208 are superimposed against one another and are substantially congruent with respect to one another. On the other hand, however, the bight 40' has a greater width and length than the bight 202,'and while the bights 40 (and 40) extend substantially perpendicular to their respective connected arms, the bights 202 connect with their respective arms at an acute angle relative to the planes thereof.

As is seen in FIG. 5, the bight 202 is displayed laterally from the bight 40 while maintaining a confronting relationship relative thereto. The width of the arm 204 is less than the width of the arm 42 but extends longitudinally for substantially the same length thereof to tenninate in a rounded end 212. The arm 204, adjacent its outer end, is provided with a transversely extending opening 214.

The pin 54 has been here modified to eliminate the opening 72. The end of the pin 56 proximate the flange 58 is, in this embodiment, enlarged to form a cylindrical abutment member 216, and spaced inwardly therefrom is an integrally formed radial flange 218. That portion of the shank 56 extending between the member 216 and the flange 218 is received through the opening 214 of the arm 204, and the bias of each spring 200 exerted against the member 216 is such that the wiping flange 58 is constantly urged to move to the left, as viewed in FIG. 5, to maintain the flange 58' in its seat 52.

Thus, the only difference between the embodiments resides in the means for achieving the spring bias on each of the switch contacts 54, 54'. All other components of the inven-- tion, their function and relationship relative to one another, remain the same. I

The switch contacts described above have been designed to ensure electrical continuity where conventional switches will not operate due to the fact that in conventional switches the contacts on either the pointer or the adjustable contact become contaminated by environmental corrosion. highly repetitive and long-life contact arcing which builds up an insulating barrier. The wipingswitch contacts of this invention have been tested and have proven to be highly satisfactory in obviating the disadvantage above noted.

Having described and illustrated two embodiments of this invention in detail, it will be understood that the same are of fered only by way of example, and that the scope of this invention is limited only by way of the appended claims.

We claim:

1. An electric switch comprising, in combination, a movable switch arm, fixed support means for a wiping switch contact disposed in the path of the movement of said switch arm, and wherein:

said support means includes seat means;

a wiping contact having a first portion disposed in the path of movement of said movable switch arm and a second portion engaging in said seat means for swivel wiping movement therein and relative thereto upon engagement of said movable switch arm with said first portion; and

means on said support means engaging said first portion to mechanically secure and electrically connect said second portion in said seat means, said engaging means cooperating with said first portion to yieldingly resist said swivel I fwiping movement of said second portion in said seat means as said movable switch arm engages said one portion-causing said wiping contact to move therewith and to return said wiping contact to its original position upon disengagement of said movable switch arm therefrom.

2. An electric switch as defined in claim 1 wherein:

said support means comprises a fixed switch arm having said seat means formed therein.

3. An electric switch as defined in claim 2 wherein:

said seat means is concave and opens in one side of said fixed switch arm; and

said second portion of said wiping contact is convex.

4. An electric switch as defined in claim 3 wherein:

said first portion comprises an elongated pin; and

said second portion includes a flange having a convex side.

5. An electric switch as defined in claim 4 wherein:

said fixed switch arm is provided with a bore extending inwardly from its opposed side and communicates with said concave seat; and

said pin extends on each side of said flange to provide an extension disposed in said bore engageable with the side of said bore to limit said swivel wiping movement of said flange upon engagement of said movable switch am with said pin.

6. An electric switch as defined in claim 5 wherein:

said means engaging said first portion comprises a flexible resilient member.

7. An electric switch as defined in claim 6 wherein:

said flexible resilient member comprises a wire spring having one of itsends connected on said fixed switch arm, and the other end of said wire connected on said pin extension.

8. An electric switch as defined in claim 7 wherein:

said pin extension is provided with an opening to receive said other end of said wire therein.

9. An electric switch as defined in claim 6 wherein:

said flexible resilient member comprises an elongated flexible leaf spring having a pair of opposed ends;

means fixedly connecting together one end of said leaf spring on said fixed switch arm; and

means loosely connecting the other end of said leaf spring on said pin extension.

1Q. An electric switch as defined in claim 9 wherein: I said last-named connecting, means includes an opening extending transversely through said other end of said leaf spring to loosely receive said pin extension therethrough; an abutment member on the outer end of said pin extension on one side of said leaf spring; and a flange on said pin extension on the other side of said leaf spring. 

2. An electric switch as defined in claim 1 wherein: said support means comprises a fixed switch arm having said seat means formed therein.
 3. An electric switch as defined in claim 2 wherein: said seat means is concave and opens in one side of said fixed switch arm; and said second portion of said wiping contact is convex.
 4. An electric switch as defined in claim 3 wherein: said first portion comprises an elongated pin; and said second portion includes a flange having a convex side.
 5. An electric switch as defined iN claim 4 wherein: said fixed switch arm is provided with a bore extending inwardly from its opposed side and communicates with said concave seat; and said pin extends on each side of said flange to provide an extension disposed in said bore engageable with the side of said bore to limit said swivel wiping movement of said flange upon engagement of said movable switch arm with said pin.
 6. An electric switch as defined in claim 5 wherein: said means engaging said first portion comprises a flexible resilient member.
 7. An electric switch as defined in claim 6 wherein: said flexible resilient member comprises a wire spring having one of its ends connected on said fixed switch arm, and the other end of said wire connected on said pin extension.
 8. An electric switch as defined in claim 7 wherein: said pin extension is provided with an opening to receive said other end of said wire therein.
 9. An electric switch as defined in claim 6 wherein: said flexible resilient member comprises an elongated flexible leaf spring having a pair of opposed ends; means fixedly connecting together one end of said leaf spring on said fixed switch arm; and means loosely connecting the other end of said leaf spring on said pin extension.
 10. An electric switch as defined in claim 9 wherein: said last-named connecting means includes an opening extending transversely through said other end of said leaf spring to loosely receive said pin extension therethrough; an abutment member on the outer end of said pin extension on one side of said leaf spring; and a flange on said pin extension on the other side of said leaf spring. 